Liquid crystal display elements now in practical use include twisted nematic (TN) mode and super twisted nematic (STN) mode. Display cells utilizing ferroelectric liquid crystals have also been proposed. These display cells essentially contain a polarizing sheet and requires orientation treatment.
There is also known a process for producing a liquid crystal device capable of making a large, bright, and high contrast display at low cost without requiring a polarizing sheet or orientation treatment, in which a polymer matrix having dispersed therein an encapsulated liquid crystal material is formed into a thin film (hereinafter referred to as polymer encapsulated type device) as disclosed in JP-A-58-501631 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and U.S. Pat. No. 4,435,047. The encapsulizing material proposed includes gelatin, gum arabic, polyvinyl alcohol, etc.
According to this technique, when liquid crystal molecules encapsulized with polyvinyl alcohol exhibit positive dielectric anisotropy in a film, they are oriented in the direction of an electric field in which they are placed, and exhibits transparency if a refractive index n.sub.O of the liquid crystal is equal to a refractive index n.sub.p of the polymer. On removal of the electric field, the liquid crystal molecules are not aligned and the refractive index of the liquid crystal droplets is shifted from n.sub.O As a result, light is scattered at an interface cf liquid crystal droplets and inhibited from transmission to make the film white turbid.
There are several other proposals using a polymer film having dispersed therein microcapsulated liquid crystal droplets. For example, JP-A-61-502128 discloses liquid crystals dispersed in an epoxy resin, and JP-A-622231 discloses liquid crystals dispersed in a specific ultraviolet-cured polymer.
In these polymer-encapsuled type devices, since the electric field effect is exerted on the liquid crystal droplets via the polymer matrix, a high drive voltage is required to change the liquid crystal molecule alignment, which has caused various problems on practical use.
Further, in order to achieve sufficient transparency on application of an electric field, special care should be taken in selecting the liquid crystal and the polymer so that they may have refractive indices approximate to each other.
Furthermore, it is difficult to achieve a large display by means of a multiplexing because there exists no threshold voltage which is necessary for realizing such a display.
These disadvantages have been a serious hindrance to putting large-area liquid crystal devices into practical use.